Influence of carbonation on the release of arsenic and lead from cementitious matrices

Sarra El Bedoui, François Duhaime, Jean-Sébastien Dubé

In the proceedings of: GeoOttawa 2017: 70th Canadian Geotechnical Conference; 12th joint with IAH-CNC

Session: Geoenvironmental II

ABSTRACT: The main objective of this study is to determine the impact of carbonation, the reaction of atmospheric CO2 with the cementitious matrix, on the leaching of arsenic and lead from stabilized and solidified (S/S) matrices. Batch leaching tests, based on thermodynamic equilibrium, were used to evaluate the solubility of these inorganic contaminants as a function of pH and at the initial pH of the non-carbonated and carbonated matrices. Phenolphthalein was used to follow pH with time during the accelerated carbonation. The results show that carbonation causes the decrease of pH of the S/S materials. Acidification of cementitious matrices led to the release of arsenic immobilized by the S/S treatment over the entire pH range. This is most likely caused by the dissolution of cement hydrates, which play an important role in the retention of inorganic contaminants. On the contrary, lead was retained in the S/S soil to a higher degree after carbonation.

RÉSUMÉ: L'objectif principal de cette étude est de déterminer l'impact de la carbonatation, la réaction du CO2 atmosphérique avec la matrice cimentaire, sur la lixiviation de l'arsenic et du plomb des matrices stabilisées et solidifiées (S/S). Les essais de lixiviation en batch, basés sur l'équilibre thermodynamique, ont été utilisés pour évaluer la solubilité de ces contaminants inorganiques en fonction du pH et au pH naturel des monolithes non carbonatés et carbonatés. La phénolphtaléine a été au cours du temps suite à la carbonatation accélérée. Les résultats obtenus montrent que la carbonatation provoque la diminution du pH des matériaux S/S. L'acidification des matrices cimentaires a entraîné fort probablement causé par la dissolution des hydrates de ciment qui jouent un rôle important dans la rétention des contaminants inorganiques. Le plomb, quant à lui, est fixé davantage par la carbonatation.

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